I have a program that generates a heightmap and then displays it as a mesh with OpenGL. When I try to add lighting, it ends up with weird square shapes covering the mesh. They are more noticeable in some areas than others, but are always there.
I was using a quad mesh, but nothing changed after switching to a triangle mesh. I've used at least three different methods to calculate the vertex normals, all with the same effect. I was doing the lighting manually with shaders, but nothing changes when using the builtin OpenGL lighting system.
My latest normal-generating code (faces is an array of indices into verts, the vertex array):
int i;
for (i = 0; i < NINDEX; i += 3) {
vec v[3];
v[0] = verts[faces[i + 0]];
v[1] = verts[faces[i + 1]];
v[2] = verts[faces[i + 2]];
vec v1 = vec_sub(v[1], v[0]);
vec v2 = vec_sub(v[2], v[0]);
vec n = vec_norm(vec_cross(v2, v1));
norms[faces[i + 0]] = vec_add(norms[faces[i + 0]], n);
norms[faces[i + 1]] = vec_add(norms[faces[i + 1]], n);
norms[faces[i + 2]] = vec_add(norms[faces[i + 2]], n);
}
for (i = 0; i < NVERTS; i++) {
norms[i] = vec_norm(norms[i]);
}
Although that isn't the only code I've used, so I doubt that it is the cause of the problem.
I draw the mesh with:
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(3, GL_FLOAT, 0, verts);
glEnableClientState(GL_NORMAL_ARRAY);
glNormalPointer(GL_FLOAT, 0, norms);
glDrawElements(GL_TRIANGLES, NINDEX, GL_UNSIGNED_SHORT, faces);
And I'm not currently using any shaders.
What could be causing this?
EDIT: A more comprehensive set of screenshots:
For the last one, the shader code is
Vertex:
varying vec3 lightvec, normal;
void main() {
vec3 lightpos = vec3(0, 0, 100);
vec3 v = vec3(gl_ModelViewMatrix * gl_Vertex);
normal = gl_NormalMatrix * gl_Normal;
lightvec = normalize(lightpos - v);
gl_Position = ftransform();
}
Fragment:
varying vec3 lightvec, normal;
void main(void) {
float l = dot(lightvec, normal);
gl_FragColor = vec4(l, l, l, 1);
}
norms
zero-initialized? You're accumulating your vectors into it without zeroing it first, though if it's zeroed elsewhere in the program that shouldn't be a problem. – genpfaultflat
for a bit could help localize the issue. Also, OpenGL lighting tends to be very buggy for me - I am usually more sure of the code i wrote myself. – Bartek Banachewicz